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July 13, 2010 -- Higher levels of vitamin D may reduce the risk of developing Parkinson’s disease, a new study suggests.

The finding builds on previous research linking low vitamin D levels to Parkinson’s, and could mean that getting more sunlight and assuring an adequate dietary intake of vitamin D may help some people ward off the neurological disorder.

Paul Knekt, DPH, and colleagues at the National Institute for Health and Welfare in Helsinki, Finland, studied 3,173 Finnish men and women between the ages of 50 and 79 who did not have Parkinson’s when the research project began in 1978 to 1980.

Participants filled out questionnaires and were interviewed about socioeconomic and health backgrounds and underwent blood tests to be analyzed for vitamin D.

After 29 years, 50 of the participants had been diagnosed with Parkinson’s disease.

Participants who had the highest levels of serum vitamin D had a 67% lower risk of developing Parkinson’s than those in the lowest 25% of the group studied.

“Despite the overall low vitamin D levels in the study population, a dose-response relationship was found,” the authors write. “This study was carried out in Finland, an area with restricted sunlight exposure, and is thus based on a population with a continuously low vitamin D status.”

Therefore, the average serum vitamin D levels in the entire studied population were about 50% of what is considered optimal.

“Our findings are thus consistent with the hypothesis that chronic inadequacy of vitamin D is a risk factor for Parkinson’s disease,” the authors say.

In the study, people with the lowest serum vitamin D levels were three times more likely to develop Parkinson's disease, compared with people with the highest levels, Knekt tells WebMD.

Sources of Vitamin D

"Part of vitamin D is made by the body when the skin is exposed to sunlight, part comes from foods like fatty fish and milk," Knekt tells WebMD by email. "A healthy diet plus outdoor exercise may thus provide the levels of vitamin D related to the lowest risk in this study."

The nutrient has been shown in the past to exert a protective effect on the brain through antioxidant activities, regulation of calcium levels, detoxification, modulation of the immune system, and enhanced conduction of electricity through nerve cells, the researchers say. Vitamin D is also known to play a role in bone health, and vitamin D insufficiency may be linked to cancer, heart disease, type 2 diabetes, and other problems.

The authors say their study suggests that chronically inadequate vitamin D levels may play an important role in the development of Parkinson’s.

The study is published in the July issue of Archives of Neurology.

Marian Leslie Evatt, MD, MS, of Emory University in Atlanta, says in an accompanying editorial that the Knekt study “provides the first promising human data to suggest that inadequate vitamin D status is associated with the risk of developing Parkinson’s disease.” She, along with the study authors, say more work is needed to determine the exact role of the nutrient and the most beneficial levels of vitamin D people should have.

Evatt writes that there is growing evidence of a connection between vitamin D and Parkinson’s, particularly from animal studies. She says the evidence is strong enough for people to take steps to make sure they are getting enough vitamin D.

In an October 2008 study, also published in the Archives of Neurology, she and colleagues at Emory also reported evidence that low blood levels of vitamin D may be linked to Parkinson’s development.